[llvm] c158ddd - Reapply [RISCV] Fold binary op into select if profitable.
Mikhail Gudim via llvm-commits
llvm-commits at lists.llvm.org
Fri Jul 14 12:31:34 PDT 2023
Author: Mikhail Gudim
Date: 2023-07-14T15:30:54-04:00
New Revision: c158ddd99eaf3f0ce712ef6e629fdd8e7e272919
URL: https://github.com/llvm/llvm-project/commit/c158ddd99eaf3f0ce712ef6e629fdd8e7e272919
DIFF: https://github.com/llvm/llvm-project/commit/c158ddd99eaf3f0ce712ef6e629fdd8e7e272919.diff
LOG: Reapply [RISCV] Fold binary op into select if profitable.
This fixes some bugs in the original commit:
(1) Operands are passed in correct order when creating new constant
and the binary operator. New tests were added to cover these cases.
(2) Check was added to see if it is safe to commute the select and the binary operator.
Reviewed By: Craig Topper
Differential Revision: https://reviews.llvm.org/D152147
Added:
llvm/test/CodeGen/RISCV/fold-binop-into-select.ll
Modified:
llvm/lib/Target/RISCV/RISCVISelLowering.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 4388bbf8ae8d8e..5a52f91b6ba6a6 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -5819,6 +5819,72 @@ static bool selectSETCC(SDValue N, ISD::CondCode ExpectedCCVal, SDValue &Val,
return true;
}
+// Transform `binOp (select cond, x, c0), c1` where `c0` and `c1` are constants
+// into `select cond, binOp(x, c1), binOp(c0, c1)` if profitable.
+// For now we only consider transformation profitable if `binOp(c0, c1)` ends up
+// being `0` or `-1`. In such cases we can replace `select` with `and`.
+// TODO: Should we also do this if `binOp(c0, c1)` is cheaper to materialize
+// than `c0`?
+static SDValue
+foldBinOpIntoSelectIfProfitable(SDNode *BO, SelectionDAG &DAG,
+ const RISCVSubtarget &Subtarget) {
+ if (Subtarget.hasShortForwardBranchOpt())
+ return SDValue();
+
+ unsigned SelOpNo = 0;
+ SDValue Sel = BO->getOperand(0);
+ if (Sel.getOpcode() != ISD::SELECT || !Sel.hasOneUse()) {
+ SelOpNo = 1;
+ Sel = BO->getOperand(1);
+ }
+
+ if (Sel.getOpcode() != ISD::SELECT || !Sel.hasOneUse())
+ return SDValue();
+
+ unsigned ConstSelOpNo = 1;
+ unsigned OtherSelOpNo = 2;
+ if (!dyn_cast<ConstantSDNode>(Sel->getOperand(ConstSelOpNo))) {
+ ConstSelOpNo = 2;
+ OtherSelOpNo = 1;
+ }
+ SDValue ConstSelOp = Sel->getOperand(ConstSelOpNo);
+ ConstantSDNode *ConstSelOpNode = dyn_cast<ConstantSDNode>(ConstSelOp);
+ if (!ConstSelOpNode || ConstSelOpNode->isOpaque())
+ return SDValue();
+
+ SDValue ConstBinOp = BO->getOperand(SelOpNo ^ 1);
+ ConstantSDNode *ConstBinOpNode = dyn_cast<ConstantSDNode>(ConstBinOp);
+ if (!ConstBinOpNode || ConstBinOpNode->isOpaque())
+ return SDValue();
+
+ SDLoc DL(Sel);
+ EVT VT = BO->getValueType(0);
+
+ SDValue NewConstOps[2] = {ConstSelOp, ConstBinOp};
+ if (SelOpNo == 1)
+ std::swap(NewConstOps[0], NewConstOps[1]);
+
+ SDValue NewConstOp =
+ DAG.FoldConstantArithmetic(BO->getOpcode(), DL, VT, NewConstOps);
+ if (!NewConstOp)
+ return SDValue();
+
+ const APInt &NewConstAPInt =
+ cast<ConstantSDNode>(NewConstOp)->getAPIntValue();
+ if (!NewConstAPInt.isZero() && !NewConstAPInt.isAllOnes())
+ return SDValue();
+
+ SDValue OtherSelOp = Sel->getOperand(OtherSelOpNo);
+ SDValue NewNonConstOps[2] = {OtherSelOp, ConstBinOp};
+ if (SelOpNo == 1)
+ std::swap(NewNonConstOps[0], NewNonConstOps[1]);
+ SDValue NewNonConstOp = DAG.getNode(BO->getOpcode(), DL, VT, NewNonConstOps);
+
+ SDValue NewT = (ConstSelOpNo == 1) ? NewConstOp : NewNonConstOp;
+ SDValue NewF = (ConstSelOpNo == 1) ? NewNonConstOp : NewConstOp;
+ return DAG.getSelect(DL, VT, Sel.getOperand(0), NewT, NewF);
+}
+
SDValue RISCVTargetLowering::lowerSELECT(SDValue Op, SelectionDAG &DAG) const {
SDValue CondV = Op.getOperand(0);
SDValue TrueV = Op.getOperand(1);
@@ -5899,6 +5965,18 @@ SDValue RISCVTargetLowering::lowerSELECT(SDValue Op, SelectionDAG &DAG) const {
if (SDValue V = combineSelectToBinOp(Op.getNode(), DAG, Subtarget))
return V;
+ if (Op.hasOneUse()) {
+ unsigned UseOpc = Op->use_begin()->getOpcode();
+ if (isBinOp(UseOpc) && DAG.isSafeToSpeculativelyExecute(UseOpc)) {
+ SDNode *BinOp = *Op->use_begin();
+ if (SDValue NewSel = foldBinOpIntoSelectIfProfitable(*Op->use_begin(),
+ DAG, Subtarget)) {
+ DAG.ReplaceAllUsesWith(BinOp, &NewSel);
+ return lowerSELECT(NewSel, DAG);
+ }
+ }
+ }
+
// (select cc, 1.0, 0.0) -> (sint_to_fp (zext cc))
// (select cc, 0.0, 1.0) -> (sint_to_fp (zext (xor cc, 1)))
const ConstantFPSDNode *FPTV = dyn_cast<ConstantFPSDNode>(TrueV);
diff --git a/llvm/test/CodeGen/RISCV/fold-binop-into-select.ll b/llvm/test/CodeGen/RISCV/fold-binop-into-select.ll
new file mode 100644
index 00000000000000..1512db87b9311e
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/fold-binop-into-select.ll
@@ -0,0 +1,60 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
+; RUN: llc -mtriple=riscv64 < %s | FileCheck %s
+
+define i64 @fold_binop_into_select_0(i1 %c, i64 %x) {
+; CHECK-LABEL: fold_binop_into_select_0:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: addi a1, a1, -2
+; CHECK-NEXT: slli a0, a0, 63
+; CHECK-NEXT: srai a0, a0, 63
+; CHECK-NEXT: and a0, a0, a1
+; CHECK-NEXT: ret
+entry:
+ %select_ = select i1 %c, i64 %x, i64 2
+ %res = sub i64 %select_, 2
+ ret i64 %res
+}
+
+define i64 @fold_binop_into_select_1(i1 %c, i64 %x) {
+; CHECK-LABEL: fold_binop_into_select_1:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: andi a0, a0, 1
+; CHECK-NEXT: addi a1, a1, -2
+; CHECK-NEXT: addi a0, a0, -1
+; CHECK-NEXT: and a0, a0, a1
+; CHECK-NEXT: ret
+entry:
+ %select_ = select i1 %c, i64 2, i64 %x
+ %res = sub i64 %select_, 2
+ ret i64 %res
+}
+
+define i64 @fold_binop_into_select_2(i1 %c, i64 %x) {
+; CHECK-LABEL: fold_binop_into_select_2:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: li a2, 2
+; CHECK-NEXT: sub a2, a2, a1
+; CHECK-NEXT: slli a0, a0, 63
+; CHECK-NEXT: srai a0, a0, 63
+; CHECK-NEXT: and a0, a0, a2
+; CHECK-NEXT: ret
+entry:
+ %select_ = select i1 %c, i64 %x, i64 2
+ %res = sub i64 2, %select_
+ ret i64 %res
+}
+
+define i64 @fold_binop_into_select_3(i1 %c, i64 %x) {
+; CHECK-LABEL: fold_binop_into_select_3:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: andi a0, a0, 1
+; CHECK-NEXT: li a2, 2
+; CHECK-NEXT: sub a2, a2, a1
+; CHECK-NEXT: addi a0, a0, -1
+; CHECK-NEXT: and a0, a0, a2
+; CHECK-NEXT: ret
+entry:
+ %select_ = select i1 %c, i64 2, i64 %x
+ %res = sub i64 2, %select_
+ ret i64 %res
+}
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